Optical tweezer techniques

The optical tweezers technique has been a powerful tool for biological application. We believe that precise control of the cellular microenvironment and single-cell analysis provide opportunities to predict the effects of external stimuli including cell-cell, cell-ECM and cell-soluble factor interaction on the cell behavior and fate, which are link to revealing the internal cellular signaling system. There still exists a broad distribution of cell responses even by single-cell analysis. Researchers need to improve and develop the technique to one utilizable for a precise analysis. The... 

Atomic force microscopy and optical tweezer techniques can be used to manipulate single macromolecules. 

Experimental techniques based on the application of mechanical forces to single molecules in small assemblies have been applied to study the binding properties of biomolecules and their response to external mechanical manipulations. Among such techniques are atomic force microscopy (AFM), optical tweezers, biomembrane force probe, and surface force apparatus experiments (Binning et al., 1986 Block and Svoboda, 1994 Evans et ah, 1995 Israelachvili, 1992). These techniques have inspired us and others (see also the chapters by Eichinger et al. and by Hermans et al. in this volume) to adopt a similar approach for the study of biomolecules by means of computer simulations. 

Near-field Raman imaging with a scanned probe has been reported [18, 19]. However, the technique is painfully slow (5-10 h, even for strong scatterers) and it has found very little use. Acquisition time can be decreased by using a polystyrene bead as a very high numerical aperture immersion lens. Working at 532 nm, Kasim et al. used a 60x/1.2 immersion aperture as an optical tweezer to simultaneously position the bead and operate it as a high NA lens [20]. They obtained a spatial resolution of about 80 nm on doped silicon with a few minutes scan time (Fig. 5.1). However, because of the need for a relatively smooth surface and a very intense scatterer, this technique is not likely to find much application in biomedical or pharmaceutical applications [21, 22],... 

Complementary to the SFA experiments, SFM techniques enabled direct, non-destructive and non-contact measurement of forces which can be as small as 1 pN. Compared to other probes such as optical tweezers, surface force balance and osmotic stress [378-380], the scanning force microscope has an advantage due to its ability in local force measurements on heterogeneous and rough surfaces with excellent spatial resolution [381]. Thus, a force-distance dependence measured from a small surface area provides a microscopic basis for understanding the macroscopic interfacial properties. Furthermore, lateral mapping... 

Vossen DLJ, Fific D, Penninkhof J, van Dillen T, Polman A, van Blaaderen A (2005) Combined optical tweezers/ion beam technique to tune colloidal masks for nanolithography. Nano Lett... 

In 1986, Ashkin and coworkers reported on the first successful single-beam gradient-force trap, or laser tweezers, for dielectric particles [21]. They were able to trap particles of glass, silica, and polystyrene (PS) in the range from 25 nm to 10 pm in water. Optical trapping techniques have since been integrated to a range of different... 

Raman probes. SERS can then be performed on optically induced aggregates of the trapped particles. Alternatively, metal nanoparticles can also be attached on micron-sized dielectric beads, which are much easier to trap. Raman probes can be adsorbed on the surface of the metal nanoparticles. In addition, combined with other techniques, such as microfluidics, the applicability of optical tweezers for SERS can be even more expanded. 

Other methods have appeared more recently for measuring forces between macroscopic surfaces or between a (large) colloidal particle and a surface, immersed in a liquid. These include the total internal reflection microscope in 1990 (TIRM) and the atomic force microscope in 1991(AFM). With TIRM, incredibly weak forces can be measured (-10 N), whilst with AFM forces - 10 N can be determined. With the development of optical tweezers, we now have the ability to measure forces directly between two colloidal particles. Using these latest techniques, not only may interaction forces between surfaces be measured but, by performing dynamic measurements, the hydrodynamic forces can also be examined. We are now at a stage surely undreamt of by Theo Overbeek 50 or so years ago when he made his own measurements. It is surely fitting that he has lived to witness all this, and that he has reached an age almost commensurate with that of the Faraday Society/Division itself ... 

This effect can be used to position and manipulate single cells or large viruses in solution. For other biophysical studies, individual macromolecules can be tethered to one or more latex or plastic beads and manipulated using optical tweezers. Other techniques combine similar approaches using small magnetic beads. 

Block, S.M. (1990). Optical tweezers a new tool for biophysics, in Noninvasive Techniques in Cell Biology, pp. 375-402. Wiley-Liss. 

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